Heat exchanger

ABSTRACT

An improved heat exchanger that effects the transfer of heat between spaced-apart members that are thermally coupled by extended and interjacence surfaces of the members.

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Umted States Patent 11113,610,334

[72] inventov Harold L. Sletten [56] Referencm Cited Northridge. Calif-UNITED STATES PATENTS [211 F J" g g 1968 813.918 2/1906 Schmitz 165/141[221 8 1 2,869,836 1/1959 Huet l65/179 x {451 Pmemed 1971 3 260 6527/1966 Ritz m1 176/81 [73] Assignee North American Rockwell CorporationPrimary ExaminerLloyd L. King Assistant Examiner-Theophil W. Slreule[54] HEAT EXCHANGER A1larneys-H. Fredrick Hamann and Donald J.Ellingsberg 10 Claims, 2 Drawing Figs.

52 u.s.c1 165/181,

250/106 ABSTRACT: An improved heat exchanger that effects the [5 1] Int.Cl F28! 1/20 transfer of heat between spaced-apart members that arether- [50] Field of Search 165/179-184, mally coupled by extended andinterjacence surfaces of the 141, l54;250/l06 S; 176/81 members.

PATENTEU am am INVENTOR.

- HAROLD L. SLETTEN I2 19 I "1 II (r 7 FIG. 2

HEAT EXCHANGER BACKGROUND OF THE INVENTION It is generally well knownthat a heat exchanger is a device that transfers heat from one place toanother by thennal coupling, i.e. and by conduction, by convection, andby radiation, or any combination thereof.

Heat is mode of transfer of energy that is used in a conventionalthermal or steam power plant. The heat is supplied to a steam-generatorthat generates steam which drives a turbinegenerator. The heat energyadded to the steam is partially converted to mechanical energy bythermodynamic expansion in the turbine, and the generator, which iscoupled to the turbine, converts the mechanical energy into electricalenergy or electricity.

Conventional steam power plants include fossil-fuel and nuclear powerplants. While fossil-fuel steam power plants generate steam by the heatof combustion resulting from the burning of solid, liquid, or gaseousfuel, nuclear steam power plants use the heat of nuclear fission togenerate steam. The thermal energy from the fission reaction istransferred as heat to water and produces steam which drives aturbine-generator set in a conventional manner.

Fission reactions occur in the nuclear fuel which is usually containedin one or more fuel assemblies that are positioned within a nuclearreactor core. The reactor core usually contains hundreds of fuelassemblies that have an economical operating life. When the capacity ofthe fuel assembly to generate or efiiciently transfer heat declines, thefuel assembly is removed from the reactor core by special fuel handlingmachines and a new fuel assembly is positioned in the core. However, theremoved fuel assembly continues to generate heat, i.e., heat produced bythe decay of the radioactive fission products, and this decay heat mustbe transferred to prevent system damage.

Conventional fuel handling systems include various methods for enhancingthe transfer ofdecay heat from the fuel assembly. For example, in oneoperating nuclear power plant, the fuel assembly was positioned in asodium-filled finned pot and the pot, which was removed from a sodiumpool, was placed in a cask car that carried the fuel assembly/pot to adecay storage area. In the car, decay heat from the fuel assembly, andthus from the finned pot, was transferred to an inert gas atmosphere.The gas atmosphere was force circulated in a closed cycle which includedan external heat exchanger integral with the cask car. However, thisforce circulated gas atmosphere carried residual sodium that had clungto the cask exterior throughout the system and deposited the sodium onthe heat exchange surfaces. This blocked the flow of the gas andimpaired heat transfer characteristics. Unless a solution could beprovided for this particular problem, damage to the system from thebuildup of decay heat (approximately eight kilowatts) would continue.

OBJECTS OF THE INVENTION Accordingly, it is an object of the inventionto provide a new and improved heat exchanger.

It is an object of the invention to provide an improved heat exchangerfor the transfer of heat primarily by natural convectron.

SUMMARY OF THE INVENTION Briefly, in accordance with one form oftheinvention, a new and improved heat exchanger is provided having an innermember cooperating with a heat source and generally telescoped within anouter member functioning as a heat sink. The inner member has aplurality of outwardly directed extended surfaces that are maintained inan interadjacent relationship with a plurality of inwardly directedextended surfaces of the outer member so that heat is transferredprimarily through radiative and natural convective thermal couplingbetween the inner and outer members.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which may be regarded as theinvention, the organization and method of operation, together withfurther objects, features, and the attending advantages thereof, maybest be understood when the following description is read in connectionwith the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front view, partly brokenaway and partly sectional, of the heat exchanger of the invention; and

FIG. 2 is a sectional view, partly broken away, along the line 2-2 ofFIG. 1.

DESCRIPTION OF THE INVENTION The heat exchanger 10 of the invention asshown by FIGS. 1 and 2 has an inner member 12 positioned or telescopedwithin an outer member 14.

The inner member 12 has a plurality of similar outwardly directedextended surfaces that in heat exchanger 10 have the form of similarfins 16 that are circumferentially spaced apart since the inner memberis a hollow right cylinder as shown. The outer member 14 has a pluralityof similar inwardly directed extended surfaces that in heat exchanger 10have the form of smaller fine 18 that are circumferentially spaced apartsince the outer member is also a hollow right cylinder that receives theinner member 12 in a telescopic manner.

The outwardly directed fins 16 of the inner member I2 are maintained ina spaced-apart or interadjacent relationship with the inwardly directedfins 18 of the outer member 14 as shown by FIG. 2. When the inner member12 is thermally coupled to a heat source, such as a fuel assembly 20containing radioactive fuel, heat energy is transferred from theoutwardly directed fins 16 to the interadjacent inwardly directed fins18 by thermal radiative and natural convective thermal coupling. Theouter member 14 can be the end heat sink or can be thermally coupled toa separate heat sink (not shown but considered conventional, eg aseparate heat exchanger). However, it is contemplated that the outermember 14 can be thermally coupled to a heat source while the innermember 12 is coupled to a heat sink.

Thennal coupling of the fuel assembly 20 to the inner member 12 can beenhanced by the introduction of a fluid such as liquid metal, e.g.sodium (Na), into the inner volume defined by the inner member so thatthe fuel assembly is substantially covered by the fluid.

As will be evidenced from the foregoing description, certain aspects ofthe invention are not limited to the particular details of'constructionas illustrated, and it is contemplated that other modifications andapplications will occur to those skilled in the art. It is contemplatedthat in certain operating conditions, e.g., where there is an absenceofliquid metal such as sodium, that forced convection can be used tofurther enhance the natural convective thermal coupling between theinteradjacent fins. It is, therefore, intended that the appended claimsshall cover such modifications and applications that do not depart fromthe true spirit and scope of the invention.

I claim:

1. An improved heat exchanger for use with a heat source, the heatexchanger comprising:

a. first means thermally coupled to the heat source,

b. first extended surface means extending from said first means,

c. heat sink means spaced apart from said first means, and

d. heat sink extended surface means extending from said heat sink means,

c. said first extended surface means and said heat sink extended surfacemeans maintained in an interadjacent relationship so that heatoriginating from the heat source passes substantially through convectiveand radiative coupling from said first extended surface means to saidheat sink extended surface means.

2. The improved heat exchanger of claim 1 in which said heat sink meansgenerally encloses said first means.

3. The improved heat exchanger of claim 1 in which said first meansgenerally encloses said heat sink means.

4. The improved heat exchanger of claim 1 in which respective ones ofsaid first means and said heat sink means are maintained in a telescopicrelationship.

5. The improved heat exchanger of claim 4 in which said first means andsaid heat sink means are generally cylindrical means.

6. The improved heat exchanger of claim 1 in which said first extendedsurface means are fin means.

7. The improved heat exchanger of claim 1 in which said heat sinkextended surface means are fin means.

8. The improved heat exchanger of claim 1 in which said heat sink meansincludes a fluid means in fluid contact with said first extended surfacemeans and said heat sink extended surface means so that heat originatingfrom the heat source passes through said fluid means from said firstextended surface means to said heat sink extended surface means.

9. The improved heat exchanger of claim 8 in which said fluid means is aliquid.

10. The improved heat exchanger of claim 9 in which said liquid is aliquid metal.

1. An improved heat exchanger for use with a heat source, the heatexchanger comprising: a. first means thermally coupled to the heatsource, b. first extended surface means extending from said first means,c. heat sink means spaced apart from said first means, and d. heat sinkextended surface means extending from said heat sink means, e. saidfirst extended surface means and said heat sink extended surface meansmaintained in an interadjacent relationship so that heat originatingfrom the heat source passes substantially through convective andradiative coupling from said first extended surface means to said heatsink extended surface means.
 2. The improved heat exchanger of claim 1in which said heat sink means generally encloses said first means. 3.The improved heat exchanger of claim 1 in which said first meansgenerally encloses said heat sink means.
 4. The improved heat exchangerof claim 1 in which respective ones of said first means and said heatsink means are maintained in a telescopic relationship.
 5. The improvedheat exchanger of claim 4 in which said first means and said heat sinkmeans are generally cylindrical means.
 6. The improved heat exchanger ofclaim 1 in which said first extended surface means are fin means.
 7. Theimproved heat exchanger of claim 1 in which said heat sink extendedsurface means are fin means.
 8. The improved heat exchanger of claim 1in which said heat sink means includes a fluid means in fluid contactwith said first extended surface means and said heat sink extendedsurface means so that heat originating from the heat source passesthrough said fluid means from said first extended surface means to saidheat sink extended surface means.
 9. The improved heat exchanger ofclaim 8 in which said fluid means is a liquid.
 10. The improved heatexchanger of claim 9 in which said liquid is a liquid metal.